Aluminum iron oxide incendiary composition containing a (cyclopentadienyl) iron compound



United States Patent 3,498,857 ALUMINUM-IRON OXIDE IN CEN DIARY COMPOSI- TION CONTAINING A (CYCLOPENTADIENYL) IRON COMPOUND Urho Albert Lehikoinen, Detroit, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Dec. 6, 1966, Ser. No. 600,006

Int. Cl. C06b 1/00 US. Cl. 149-21 11 Claims ABSTRACT OF THE DISCLOSURE Bis(cyclopentadienyl)iron and bis(alkylcyc1opentadienyl)iron compounds (also known as ferrocene-type compounds) improve the ignition and burning properties of thermites and thermates. Preferred thermites are composed of powdered aluminum and an iron oxide. In addition to these ingredients, the thermates contain materials such as flake aluminum, sulfur, hydrocarbon oils, and oxidizers such as barium nitrate. The improved compositions are useful in incendiary weapons, as munitions or as starters for other pyrotechnic materials.

This invention relates to improved pyrotechnic compositions for incendiary munitions. More specifically, the improvement relates to compositions known as thermites and thermates.

Typically, thermites are mixture of powdered aluminum and iron oxide. Broadly speaking, however, thermites may also be mixtures of magnesium and iron oxide, zirconium and iron oxide, and the like. Upon ignition, thermites undergo strongly exothermic reactions. For example, magnetite reacts with aluminum as follows:

3FE304+ 4Al203 +9Fe+heat Red iron oxide, Fe O reacts with aluminum in a similar manner. Therefore, it may also be employed in thermites. These reactions are Well-known in the art.

Generally, thermites have a major deficiency; they are not readily ignitable. Various additives which decrease the ignition temperature are known in the art. Thermites modified with these additives are in military use and are called thermates. Thus, typical thermates contain metalmetal oxide systems such as those mentioned above and, in addition, contain oxidizers such as barium nitrate, potassium chromate and potassium permanganate. Other components used in thermates are sulfur, hydrocarbon oils, zinc powder, magnesium powder, and the like. Although these additives somewhat lower the ignition temperature and accelerate burning, the improvement is only partial and not totally satisfactory.

Since thermites and thermates presently available are often unsatisfactory, an object of this invention is to prepare said materials having superior igniting and burning properties. Further objects will be apparent from the following detailed description and appended claims.

The objects of this invention are accomplished by incorporating in conventional thermites and thermates one or more compounds having the following general formula:

3,498,857 Patented Mar. 3, 1970 atoms. Said aliphatic groups can be straight or branched chains and can have one or more olefinic bonds. Nonlimiting examples of compounds described by the above general formula are bis(cyclopentadienyl)iron, (cyclopentadienyl) (methylcyclopentadienyl)iron, (cyclopentadienyl) (ethylcyclopentadienyl iron, bis (propylcyclopentadienyl)iron, bis(isopropylcyclopentadienyl)iron, bis- (butylcyclopentadienyl)iron, bis(tert butylcyclopentadienyl)iron, bis(hexylcyclopentadienyl)iron, bis(methylcyclopentadienyl) iron, (cyclopentadienyl) (dimethylcyclopentadienyl iron, bis (ethylcyclopentadienyl iron, and cyclopentadienyl) (diethylcyclopentadienyl)iron, and the like. The above compounds, also known as ferrocene-type compounds, illustrate that both symmetrical and unsymmetrical alkyl ferrocenes may be employed. By symmetrical and unsymmetrical is meant alkyl ferrocenes with heteroannular and homoannular substitution respectively. Ferrocene and alkyl ferrocene polymers may also be employed in this invention.

The most preferred compounds defined by the above formula are bis(cyclopentadienyl)iron and the alkyl derivatives thereof having 11 to 14 carbon atoms, such as (cyclopentadienyl)(methylcyclopentadienyl)iron, bis- (methylcyclopentadienyl)iron and (cyclopentadienyl) dimethylcyclopentadienyl iron, cyclopentadienyl) (ethylcyclopentadienyl iron, bis (ethylcyclopentadienyl) iron, and (cyclopentadienyl)(diethylcyclopentadienyl) iron.

Any ignition and combustion-improving amount of a ferrocene-type compound may be incorporated in thermites and thermates of this invention, although 2 to. 50 weight percent of the total composition is generally found to be adequate. A more preferred amount of a ferrocenetype compound is from about 10 to about 35 weight percent of the total composition.

The improvement of ignition and burning properties of thermites and thermates is illustrated in Table 1 below. Table 1 shows how ignition and combustion properties of various compositions were consistently improved when ferrocene was added. Every example in Table 1 shows the results obtained when a pyrotechnic material in a powdered form was wetted with toluene and thereafter ignited. Magnesium ribbon is generally employed as a starter for thermites and thermates. However, toluene was used as a starter in the tests reported in Table 1 because of convenience. Each example demonstrates the improved ignition and combustion properties obtained when the specified amount of bis(cyclopentadienyl)iron (ferrocene) was added to the pyrotechnic composition first tested without ferrocene. The thermite employed in the pyrotechnics reported in Table 1 had the following composition: aluminum, 25.2 weight percent, and iron oxide (Fe O 74.8 weight percent.

TABLE 1.IGNITION AND COMBUSTION OF POWDERED TIIERMITE AND THERMATE COMPOSITIONS Composition, parts by weight Aluminum Zinc Magnesium Example No. Thermite KzCrOi B3.(NO3)2 Ferrocene flake powder powder Comments 1 1 1 Did not burn.

1 Brief flare. Very little material burned.

Did not burn.

Small flares. Very little material burned.

Did not burn.

,. Burned completely.

1 About 85% of charge burned.

l Did not burn. 1 About 30% of charge burned.

Did not burn. 1 Burned completely.

1' Brief flare-ups, very little burned, 1 About 50% of charge burned.

In the above examples, analytical grade crystalline Ba(NOa)z was employed.

Similar results are obtained when, in the above examples,

( cyclopentadienyl) (methylcyclopentadienyl) iron, (cyclopentaclienyl) (hexylcyclopentadienyl) iron,

bis propylcyclopentadienyl iron,

bis tert-butylcyclopcntadienyl) iron,

bis (methylcyclopentadienyl iron,

(cyclopentadienyl) (dimethylcyclopentadienyl) iron, and bis (dihexylcyclopentadienyl iron are substituted for his (cyclopentadienyl)iron (ferrocene).

The above table, thus, clearly shows that the ignition of the compositions containing ferrocene-type compounds is improved and that the burning of these compositions is much more complete. The improvement of the ignition and burning properties attributed to ferrocene is more outstanding in pelletized thermates as shown in Example 7 below.

EXAMPLE 7 Two pyrotechnic compositions were prepared separately. One was the thermite composition employed in Table 1, above, having 252 weight percent of powdered aluminum and 74.8 percent of iron oxide (FBzOg). The other composition contained one part by weight of the above-mentioned thermite, one part by weight of potassium permanganate, one part by weight ferrocene, and 0.5 part by weight zinc powder. Solid pellets /2" O.D., /8" thick) were prepared in such a manner that one-half of each pellet consisted of the thermite composition and the other half consisted of the thermate composition containing ferrocene. The pellets were wetted with toluene and ignited. The portion of each pellet consisting of the ferocene-containing thermate composition ignited immediately and burned cmpletely. However, the thermite portion of the pellet which did not contain ferrocene did not burn at all.

Table 2 below shows the improved ignition and burning properties of additional thermates containing ferrocene. These thermates have been pelletized to form hollow-core pellets 3 O.D., I.D., thick). The pellets were saturated with toluene and ignited. The composition of the thermite employed in the thermates reported in Table 2 was the same as that employed in the thermates reported in Table 1.

TAB LE 2 Similar results are obtained when, in Examples 7 to 10, (cyclopentadienyl) (mcthylcyclopentadienyl) iron, (cyclopentadienyl) (ethylcyclopentadienyl iron, bis (propylcyclopentadienyl)iron, bis(tert-butylcyclopentadienyl) iron, and bis(methylcyclopentadienyl)iron and (cyclopentadienyl) (dimethylcyclopentadienyl)iron are substituted for bis (cyclopentadienyl)iron (ferrocene) Considering the fact that even finely divided thermates which have a large surface area are not easily ignited, it is most startling that pelletized thermates, which have a very small surface aera, can be ignited and burned with such case as demonstrated in Example 7 and in Table 2 above.

Thermates and thermites improved by the addition of ferrocene-type compounds may be employed in the same manner and for the same purposes as conventional thermates. The most widely known uses of thermates and thermites are as incendiary materials in munitions or as starters for other incendiary materials which are more difficult to ignite. An example of said use is in a magnesium aerial bomb which is filled with a thermite or a thermate. Another example of the use of the compositions of this invention is in napalms. More specifically, a napalm having the following composition would be useful in military applications: 35 Weight percent of a pelletized thermate composed of 1 part by weight of a thermite (74.8 wt. percent of Fe O and 25.2 wt. percent of powdered aluminum), 1 part by weight of potassium permanganate and 1 part by weight of ferrocene; dispersed in 65 weight percent of conventional napalm (gasoline gelled in soap or heavy metal soa mixtures).

It was stated above that, in the tests reported in the preceding examples, toluene was employed as a starter. The thermite and thermate compositions of this invention exhibit the same improved incendiary properties when starters generally employed in military applications, such as magnesium ribbon, are used.

Having fully disclosed the novel composition and processes of this invention and their use, it is desired that this invention be limited only within the lawful scope of the appended claims.

I claim:

1. In a pyrotechnic composition selected from the group consisting of iron oxide-aluminum based thermites and thermates, the improvement consisting essentially of the addition of two to weight percent of the total Parts by weight Thermite KMnO4 Ferrocene Comments time, 5 to 7 seconds.

composition of an ignition-improving compound having the general formula:

R: R 1 R 4 thermite comprises 25 to 28 weight percent of powdered aluminum and 72 to 75 weight percent of an iron oxide selected from the group consisting of magnetite, Fe O and red iron oxide, Fe O 5. The composition of claim 4 wherein said ignitionimproving compound is selected from the group consisting of bis(cyclopentadienyl)iron, (cyclopentadienyl) (methylcyclopentadienyl) iron, cyclopentadienyl) (ethylcyclopentadienyl iron, bis (methylcyclopentadienyl iron, (cyclopentadienyl) (dimethylcyclopentadienyl) iron, bis (ethylcyclopentadienyl)iron, and (cyclopentadienyl) (diethylcyclopentadienyl) iron.

6. The composition of claim 4 wherein said ignitionimproving compound is bis(cyclopentadienyl)iron.

7. The composition of claim 5 wherein the amount of said ignition-improving compound is from about to about 35 weight percent of the total composition.

8. The composition of claim" 1 wherein said thermate comprises 60 to 80 weight percent of a thermite containing to 28 weight percent of aluminum powder and 72 to 75 weight percent of an iron oxide,

0 to 4 weight percent of flake aluminum,

0 to 5 weight percent of sulfur,

10 to 30 weight percent of an oxidizer selected from the group consisting of barium nitrate, potassium permanganate, and potassium chromate,

0 to 10 Weight percent of zinc powder, and

0 to 10 weight percent of magnesium powder.

9. The composition of claim 7 wherein said ignition improving compound is selected from the group consisting of bis(cyclopentadienyl)iron, (cyclopentadienyl) (methylcyclopentadienyl)iron, (cyclopentadienyl) (ethylcyclopentadienyl iron, bis (methylcyclopentadienyl) iron, (cyclopentadienyl) (dimethylcyclopentadienyl) iron, bis (ethylcyclopentadienyl)iron, and (cyclopentadienyl)(diethylcyclopentadienyl iron.

10. The composition of claim 8 wherein the amount of said ignition-improving compound is from about 10 to about weight percent of the total composition.

11. The composition of claim 10 wherein said ignitionimproving compound is bis(cyclopentadienyDiron.

References Cited UNITED STATES PATENTS 3,254,996 6/1966 MacDonald 14937 XR 3,297,503 1/1967 Hoffmann et a1. 14937 XR 3,309,249 3/1967 Allen 14937 XR 3,325,316 6/1967 MacDonald 149-37 XR 3,344,210 9/1967 Silvia 149-37 XR CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, JR., Assistant Examiner US. Cl. X.R. 149-41, 43 44, 61 

